IDENTIFYING SOURCE AREAS FOR FLOW AND HEAT IN THE KUPARUK RIVER, ALASKA

Arctic rivers provide substantial amounts of freshwater and heat to the Arctic Ocean, with potential implications for coastal ecology, shoreline processes, and sea ice dynamics. Predicting how changes in climate will affect these advective fluxes requires an understanding of the source areas and mechanisms that contribute to water and heat exported from Arctic rivers. To determine the source areas of summertime mass and heat export from the Kuparuk River, Alaska to the Beaufort Sea, we analyzed discharge and river temperature data from nine gauging stations in the Kuparuk River watershed from July 2014 and July 2015. Mass and heat export at each gauging station was estimated by temporally integrating discharge and advective heat fluxes. Contributions from each subbasin were isolated by differencing inflows and outflows of main channel mass and heat recorded at the corresponding upstream and downstream boundaries. These contributions represent the net effects of all mass and heat fluxes for each river reach, and are expressed as percentages of the total exports at the most-downstream gauging station. Preliminary results show that 78% of mass and 91% of heat exported from the Kuparuk River originated in two subbasins in the mid-section of the watershed that account for 63% of the total watershed area. A subbasin completely on the coastal plain (17% of watershed area) contributed 5% of mass and 7% of heat. The subbasin closest to the coast (11% of watershed area) provided 6% of the mass, and reduced heat export by 7%. The remaining 11% of mass and 9% of heat entered the Kuparuk River in the foothill subbasins, which account for 9% of the watershed area. These findings provide new insights into the spatial distribution of mass and heat source areas within the watershed. Specifically, the region between the foothills and the coastal plain provided the vast majority of mass and heat exported by the Kuparuk River, while the subbasin closest to the coast acted as a heat sink, removing heat from the river before it reached the Ocean. Determining the mechanisms responsible for subbasin contributions is necessary to understand the implications of changes in climate on total watershed mass and heat export, and is the focus of ongoing research.